1. Field of the Invention
The present invention relates generally to the field of reciprocating engines, and more specifically, to an improved piston with radially-oriented and tapered grooves on the piston head.
2. Description of the Related Art
Most automobile engines are internal combustion engines in which the fuel burns in a plurality of combustion chambers inside of an engine block. Directly beneath each combustion chamber is a cylinder, and most engines have four, six or eight cylinders. A piston moves up and down (reciprocates) inside of each cylinder, and the piston face (or top surface) forms the floor of the combustion chamber. In a typical engine, the number of cylinders equals the number of pistons.
When the air-fuel mixture inside of the combustion chamber ignites, the explosive force pushes the piston downward. Each piston is connected to a crankshaft by a connecting rod. The pistons are configured on the crankshaft such that the downward force of one or more pistons causes one or more other pistons to move upward, thereby compressing the air-fuel mixture inside of the combustion chamber. Each combustion chamber has a port for an intake valve, an exhaust valve, and a spark plug. In a properly functioning engine, the spark plug delivers a spark to the combustion chamber when the piston is nearly at its upward-most position within the combustion chamber during the compression stroke.
A typical engine comprises four “strokes,” which refer to the up-and-down motion of the piston: intake, compression, power and exhaust. During the intake stroke, the piston moves downward as the air-fuel mixture is introduced into the combustion chamber through the intake valve. During the compression stroke, the piston moves upward and compresses the air-fuel mixture. During the power stroke, the air-fuel mixture has ignited, creating the explosive force that drives the piston downward. During the exhaust stroke, the piston moves upward, pushing the exhaust fumes through the exhaust valve.
The present invention is not limited to four-stroke (or four-cycle) engines, however. The present invention could also be used with a two-stroke (or two-cycle) engine in which the end of the combustion stroke and the beginning of the compression stroke happen simultaneously and the intake and exhaust functions are performed at the same time.
The air-fuel mixture is introduced into the combustion chamber in one of two ways—by a carburetor or a fuel injection system. With a carburetor, the air-fuel mixture is drawn or sucked into the combustion chamber through the intake valve as the piston moves downward, thereby decreasing the pressure in the combustion chamber. At start-up of the engine, the ratio of air to fuel in the air-fuel mixture is controlled by a choke plate that is situated just inside of the carburetor throat. Gasoline is drawn into the air flow inside of the carburetor from a fuel bowl inside the carburetor between the carburetor throat and the throttle valve. The throttle valve controls the flow of the air-fuel mixture into an intake manifold, which in turn holds the air-fuel mixture until it is drawn into the combustion chambers by the pressure differential created by the downwardly moving pistons.
With a fuel injection system, gasoline is sprayed directly into the combustion chamber (direct fuel injection), into the intake manifold port in the intake manifold outside of the combustion chamber (ported fuel injection), or into a carburetor body (throttle body fuel injection). The present invention, which is a modified piston design, can be used with engines that have carburetors or fuel injection systems.
In a conventional reciprocating engine (i.e., one that does not utilize the present invention), not all of the air-fuel mixture that is introduced into the combustion engine is burned or combusted. This lack of combustion results in environmentally harmful emissions. The greater the percentage of air-fuel mixture that is combusted, the lower the emissions—and vice versa.
Various methods of reducing emissions have been invented over time, and a thorough review of all such inventions is beyond the scope of this application; however, four notable attempts at reducing emissions include positive crankshaft ventilation, exhaust gas recirculation, the air injection method, and the catalytic converter. With positive crankshaft ventilation and exhaust gas recirculation, polluting exhaust fumes are added to the air-fuel mixture and burned a second time. The air injection method involves pumping fresh air into the exhaust manifold to increase oxidation and destroy harmful hydrocarbons. Catalytic converters contain compounds that react with hydrocarbons in exhaust gases to convert them to less harmful compounds. The present invention is more efficient than any of these emissions reduction methods and may eliminate the need for catalytic converters altogether.
One of the problems with conventional reciprocating engines is that there is a stagnant layer of air-fuel mixture on the face (or top surface) of the piston. This layer is often referred to as the “boundary layer,” and it adversely affects the distribution of fuel, flame front propagation, and exhaust gas flow out of the combustion chamber. It also adversely affects other aspects of the dynamic flow of air into, through and out of the combustion chamber. This is because the boundary layer is relatively stagnant and has a relatively higher viscosity than that of the air-fuel mixture adjacent to it in the combustion chamber. Some of the adverse effects of this boundary layer are described more fully below.
First, the boundary layer (which is a layer of air-fuel mixture) allows precipitation of fuel from the air-fuel mixture. The precipitated fuel gravitates onto the top of the piston, particularly around the edges (periphery) of the piston. This pooling of fuel prevents complete fuel combustion from occurring.
Second, the flame front is hindered by the difference in viscosity of the boundary layer relative to the rest of the gasses in the combustion chamber. The hydrocarbons in the fuel tend to create a carbon build-up that adheres to the top of the piston, further hindering proper combustion. If not sufficiently cooled, the hydrocarbon residue will pre-ignite the next air-fuel charge that enters the combustion chamber.
Third, the boundary layer continues to combust during the exhaust stroke of the engine, thereby allowing unburned or incompletely burned fuel to be purged into the exhaust stream. This can lead to combustion occurring in the exhaust system, which is undesirable.
Fourth, the boundary layer interferes with evacuation of the exhaust gasses because of its relatively higher viscosity and the fact that it resides on top of the piston. It also hinders the incoming air-fuel mixture that is drawn or blown into the combustion chamber during the intake stroke.
The present invention solves all of the problems created by the boundary layer on the face of the piston by directing (or shooting) the air-fuel mixture across the surface of the piston and toward the center of the piston, where the spark plug is located. This rapid redirection of the air-fuel mixture wipes the boundary layer off the surface of the piston (i.e., disrupts it) and/or prevents it from forming. Although other inventions have been designed to create general turbulence in the combustion chamber, none of these inventions is specifically directed toward shooting or directing the air-fuel mixture toward the center of the piston through the use of radially configured grooves whose depth and width are specifically tailored to create this shooting action.
Examples of invention designed to create turbulence within the combustion chamber include U.S. Pat. No. 4,063,537 (Lampredi, 1977) (describing a secondary chamber in a combustion chamber for a diesel engine, wherein a central channel induces turbulence in the combustion gasses, and grooves in the piston crown trap gasses escaping from the central channel); U.S. Pat. No. 5,065,715 (Evans, 1991) (providing a piston with a central bowl and a plurality of squish jet channels circumferentially spaced about the bowl, the purpose of the jet channels being to direct air-fuel mixture into the bowl and to create turbulence within the bowl); U.S. Pat. No. 6,047,592 (Wirth et al. 2000) (disclosing a modified piston with two longitudinal guiding ribs and a cross-guiding rib (to form an H-shaped configuration), one of the purposes of which is to form a tumble flow during the suction (intake) phase and transform the tumble flow into increased turbulence during the late compression phase); U.S. Pat. No. 6,170,454 (McFarland et al., 2001) (describing a piston with a raised portion increasing in height from the center of the piston toward the perimeter and with a plurality of dimples on the raised portion for creating eddies (or turbulence) within the air-fuel mixture); and U.S. Pat. No. 7,810,479 (Naquin, 2010) (in a preferred embodiment, providing a piston with three parallel grooves extending across the width of the piston face, the inventor claiming that combustion efficiency of an engine is related to the level of turbulence in the combustion chamber and that fluid flow is converted from laminar to turbulent when it exits the grooves in the piston face).
U.S. Pat. No. 4,471,734 (Showalter, 1984) discloses a modified piston top comprising long and short slots arranged in a radial configuration. The slots are designed to break up the roll-up vortex that forms on the top of the piston starting at the cylinder wall. (The vortices of the present invention start at the center of the piston.) This roll-up vortex is described as a direct consequence of the relative motion between the piston and the boundary layer near the surface of the cylinder (presumably the cylinder wall). These vortices are the exact opposite of the vortices created by the present invention in that they move radially inward (the vortices of the present invention move radially outward). According to the inventor, the hydrocarbons in these vortices do not burn; therefore, the purpose of the invention is to break up these vortices and create turbulence within the combustion chamber.
U.S. Pat. Nos. 7,581,526 (Lehmann, 2009) and 7,721,704 (Lehmann, 2010) involve a piston design with a plurality of vanes extending “axially,” which the inventor has defined as in the direction of the thrust line of the piston (i.e. the vanes extend upwardly from the piston face). Each vane comprises two walls. The walls may be planar or curved, and they may intersect one another or be joined by a connecting surface (as in a plateau on the top of a mountain). In one embodiment, the vanes are arranged in a radial configuration. In all embodiments, the distance between the walls of the vane is greater proximate the piston (nearest the piston face) than at the distal end of the vane (farthest from the piston face). The vanes are part of a device that is attached to the top surface of the piston crown by welding, bolts or other connecting means; in an alternate embodiment, the piston and device are unitary in construction. According to the inventor, the vanes may differ in height on a single device. The vanes create vortices in the air-fuel mixture in the combustion chamber, and these vortices are more perpendicular than parallel to the direction of movement of the piston.